Cool burning smokeless powder composition containing nitramine ethers

ABSTRACT

COOL BURNING SMOKELESS POWDER COMPOSITIONS PROVIDING HIGH IMPETUS WITH FLAME TEMPERATURES NOT EXCEEDING ABOUT 2900*K. ARE DISCLOSED. THESE SMOKELESS POWDER COMPOSITIONS CONTAIN NITROCELLULOSE, ABOUT 20% NITRAMINE ETHER AND OPTIONALLY CAN CONTAIN NITRAMINE AZIDES.

United States Patent Olfice 3,697,341 Patented Oct. 10, 1972 3,697,341 COOL BURNING SMOKELESS POWDER COMPOSI- TION CONTAINING NITRAMINE ETHERS Ronald Rosher and Ronald L. Simmons, Cumberland, 151%., assignors to Hercules Incorporated, Wilmington,

e No Drawing. Filed Aug. 29, 1969, Ser. No. 855,463 Int. Cl. C06b 15/02 U.S. Cl. 149-92 6 Claims ABSTRACT OF THE DISCLOSURE Cool burning smokeless powder compositions providing high impetus with flame temperatures not exceeding about 2900 K. are disclosed. These smokeless powder compositions contain nitrocellulose, about 20% nitramine ether and optionally can contain nitramine azides.

This invention relates to smokeless powder compositions for use in small arms and cannon suitable for applications requiring cool burning compositions, i.e., compositions having a flame temperature not exceeding about 2900 K. More particularly, this invention relates to smokeless powder compositions comprising nitrocellulose and low molecular weight nitramine ethers and nitramine azides in selected amounts.

Virtually all gun propellants in use today are based on nitrocellulose as the primary source of gas and energy. When nitrocellulose is employed alone or with ballistic modifiers, the resulting powder is referred to as a single base composition. When nitroglycerin or another liquid nitric ester is added to the composition to raise the energy thereof, the resulting powder is referred to as a double base composition. The increase in energy derived in double base compositions results from a higher flame temperature of the powder. The moles of gas generated per unit weight of double base powder is less that the number of moles of gas generated for a comparable weight of single base powder. Table I below contains data on smokeless powder compositions illustrating the effect of the use of nitroglycerin on flame temperature in smokeless powder compositions and on the moles of gas generated per gram of powder when the powder is burned.

TABLE I Nitrocellulose Nitro- (13. 15% Moles glycerin nitrogen) Flame gas gram Propel- (weight (weight temp. propel- Impetus lent percent) percent) K.) lant (it.'lb./lb.)

*Propellant compositions contain small amounts of stabilizers, residual solvents, additives. It is readily seen that as the percentage of nitroglycerin in the powder increases, that both the flame temperature and impetus of the powder increase while the moles of gas per gram of powder decrease.

Accordingly, it is an object of this invention to provide cool burning smokeless powder compositions having flame temperatures not exceeding about 2900 K, which have higher impetus at flame temperature than is possible with conventional single base and double base smokeless powder compositions.

Other objects of this invention will, in part, be obvious and will, in part, appear hereinafter. For a complete understanding of the nature and objects of this invention, reference is made to the following detailed description.

In accordance with this invention smokeless powder compositions having a maximum flame temperature of about 2900 F. are provided comprising by weight from about 35% to about nitrocellulose; from about 20% to about 65% of nitramine ethers selected from the group consisting of l,6-dimethoxy-2,S-dinitrazahexane; 1,S-dimethoxy-2,4-dinitrazapentane and mixtures thereof; and from about 0% to about 40% of nitramine azides selected from the group consisting of 1,6-diazido-2,5- dinitrazahexane; 1,7diazido-2,4-6-trinitrazaheptane and mixtures thereof.

The nitramine ethers perform two functions in the smokeless powder compositions of this invention. First, the nitramine ethers lower the flame temperature of the compositions and second, they generate a larger proportion of hydrogen and lower molecular weight combustion products than conventional smokeless powder ingredients. The nitramine azides employed in these smokeless powder compositions generate a larger proportion of hydrogen and low molecular weight combustion products than conventional smokeless powder ingredients but also raise the burning temperature of the compositions.

The following examples more fully illustrate the smokeless powder compositions of this invention. All parts and percentages are by weight unless otherwise specified. Example 1 illustrates a method for preparation of nitramine azides such as l,6-diazido-2,S-dinitrazahexane employed in the smokeless powder compositions of this invention.

EXAMPLE 1 About 525 parts of glacial acetic acid and 150 parts of trioxymethylene are placed in a flask equipped with a gas inlet tube, a mechanical stirrer and a reflux condenser fitted with a drying tube. The mixture is agitated and dry HCl gas is passed through the resulting suspension until only a slight turbidity remains. The HCl treatment is interrupted while 150 parts of dry powdered ethylene dinitramine is added to the mixture over a period of several minutes. Treatment with HCl is then resumed and the temperature slowly brought to 40 C. After approximately 2 hours, a white precipitate begins to form and the addition of HCl is continued for another hour. The mixture is allowed to stand 12 hours. The resulting nitramine chloride product which is 1,6-dichloro-2,5-dinitrazahexane, referred to hereinafter as DCDNH, is separated by filtration and washed with about 300 parts of cold glacial acetic acid. The washed DCDNH is slurried with about 200 parts of cold benzene prior to drying in a vacuum desiccator at ambient temperature. A yield of 7075% of DCDNH, having a melting point range of 105108 C. is obtained.

Twenty parts of DCDNH is dissolved in parts of anhydrous acetone and the solution is cooled in an icesalt bath to 0-10- C. The solution is blanketed with nitrogen, and 21 parts of sodium azide dissolved in 75 parts of water is added slowly to the DCDNH solution over a 30 minute period. The crystalline product is 1,6- diazido-2,5dinitrazahexane, referred to hereinafter as DADNH. The DADNH is allowed to stand overnight in contact with the mother liquor after which solid DADNH is filtered, washed three times with ice water and dried in a vacuum desiccator. The product DADNH is recrystallized from hot benzene twice and dried in a vacuum desiccator. The product yield is about 70%. The product has a melting point range of 76-77 C.

The following example illustrates a method of preparation of nitramine ethers and in particular 1,6 dimethoxy 2,5 dinitrazahexane (DMDTH) employed in the smokeless powder compositions of this invention.

3 EXAMPLE 2 The procedure of Example 1 is repeated for preparation of 1,6 dichloro 2,5 dinitrazahexane (DCDNH). About 1300 parts of methanol is heated to 40 C. and 200 parts of DCDNH is admixed with the methanol and dissolves therein. A white precipitate of DMDTH quickly forms. The temperature rises to about 48 C. within 2-3 minutes. The resulting mixture is chilled to C. and the DMDTH is collected on a Buchner funnel. The DMDTH is recrystallized twice from about 1500 parts of methanol. The product is filtered and dried in a vacuum desiccator. The product yield is about 70% and the melting point range is 7678 C.

The following example illustrates preparation of a smokeless powder composition of this invention employing nitramine azide and nitramine ether as prepared in Examples 1 and 2 respectively.

EXAMPLE 3 A smokeless powder composition is prepared having the following composition:

Percent Nitrocellulose (12.6% nitrogen) 35 DMDTH .31

DADNH 33 Diphenylamine 1 This smokeless powder composition can be prepared employing conventional smokeless powder mixing equipment and procedures. The solvent employed in mixing this composition comprises 60% ethyl alcohol and 40% acetone. The composition is prepared in a mixer maintained at 78 F. The stepwise mixing procedure employed is as follows:

(1) Add 105 parts nitrocellulose, 3 parts diphenylamine and 200 parts solvent to a mixer and mix for fifteen minutes.

(2) Add 93 parts of DMDTH to the mixer and continue mixing for 8 minutes.

(3) Add 130 parts solvent and mix for an additional minutes.

(4) Add 99 parts of DADNH and 30 parts solvent to the mixer and mix for an additional minutes.

(5) Allow mixed solvent to evaporate from the resulting smokeless powder composition of step 4 for 40 minutes.

The powder composition is extruded at 250 psi. into strands having a diameter of about 0.050 inches and cut into granules having a length of about 0.046 inches. The granules are cured for 3 days at 140 F. The powder composition is characterized. Results of the characterization of the composition is set forth in Table 11 below.

TABLE II Powder characterization: Example 1 Moles gas/gram propellant 0.049 Flame temperature, K. 2700 Heat of explosion, cal./gm 851 Stability, Taliani at 93 C. (mm. after 23 hrs.) 11 Irnpetus, (ft.-lb./lb.) 382,000

1 Calculated value.

The following examples illustrate the effect of varying the levels of DMDTH (nitramine ether) on the impetus and flame temperature of the smokeless powder compositions of this invention.

EXAMPLES 4-6 Smokeless powder compositions are prepared following the mixing procedure of Example 3. The powder compositions and results from characterization of these-compositions is set forth in Table III below.

*Calculated values.

As can be seen from review of Table III, the flame temperature for a smokeless powder composition of this invention (Example 4) is substantially the same as the flame temperature for the control powder, while moles of gas per gram of powder and impetus are substantially higher for the powder composition of this invention. Comparison of Example 5 with the control powder shows that substantially the same impetus can be obtained from a smokeless powder composition of this invention as the control propellant while the flame temperature is reduced by 357 F. Example 6 illustrates the cooling effect of DMDTH on flame temperature of the nitrocellulose based compositions while maintaining a reasonable impetus level.

From the foregoing examples it is readily apparent that the powder compositions of this invention provide flexibility in formulating a smokeless powder composition for cool burning applications. The amount of nitramine ether employed in this invention must, however, be at least 20% by weight of the powder composition in order to maintain the powder flame temperature no higher than 2900 K., since the cooling effect of the nitramine ethers is not obtained until the quantity of nitramine ether in the formulation reaches this level. It is similarly true that the maximum amount of nitramine azide in the powder compositions must not exceed 40% by weight of the powder composition in order to limit the powder flame temperature since the nitramine azides have the effect of raising the flame temperature of the composition. The minimum amount of nitrocellulose which can be employed in the smokeless powder compositions of this invention is limited by processability of the compositions and is about 35% The smokeless powder compositions of this invention can be prepared following conventional processing procedures employed in manufacture of conventional single base or double base powder compositions. Any of the well-known solvent mixtures employed in manufacture of smokeless powder such as ethyl alcohol/ acetone or ethyl alcohol/methylethylketone can be employed. The nitrocellulose employed can contain from about 12.6% nitrogen to about 13.25% nitrogen. Smokeless powder grade nitrocellulose containing about 13.15% nitrogen is preferred. Any of the well-known stabilizers for smokeless powder such as diphenylamine, ethyl centralite and the like can be employed in the compositions.

What we claim and desire to protect by Letters Patent 1s:

1. A smokeless powder composition having a maximum flame temperature of about 2900 K., said composition comprising by Weight: (a) from about 35% to about nitrocellulose, (b) from about 20% to about 65% of a nitramine ether selected from the group consisting of 1,6 dimethoxy 2,5 dinitrazahexane; l,5-dimethoxy 2,4 dinitrazapentane and mixtures thereof, and (c) from about 0% to about 40% of nitramine azides selected from the group consisting of 1,6 diazido-2,5- dinitrazahexane; 1,7 diazido 2,4,6 trinitrazaheptane, and mixtures thereof.

2. The compositions of claim 1 wherein the nitramine ether is 1,6 dimethoxy 2,5 dinitrazahexane.

3. The composition of claim 2 wherein the nitramine References Cited azide is 1,6-diazido 2,S-dinitrazahexane. UNITED STATES PATENTS 4. The composition of claim 1 wherein the mtramme 3,311,513 3/1967 Forrest 149-96 X ether is 1,6 dimethoxy 2,5 dinitrazahexane and the nitramine azide is 1,7 diazido 2,4,6 trinitrazaheptane. 5

5. The composition of claim 1 wherein the nitramine ether is 1,5 dimethoxy 2,4 dinitrazapentane and the CARL QUARFORTH Pnmary Exammer 3,317,361 5/1967 Hopper et a1 149-96 X nitramine azide is 1,6 diazido 2,5 dinitrazahexane. S. J. LECHERT, 111., Assistant Examiner 6. The composition of claim 1 wherein the nitramine ether is 1,5 dimethoxy 2,4 dinitrazapentane and the 10 115- X-R- nitramine azide is 1,7 diazido 2,4,6 trinitrazaheptane. 100 

